Sitemaps: preserve linebreaks

[kraftbj]

Fixes #9750

Proposed changes:

• Preserve linebreaks in the sitemap to make it easier for HEs to debug.

Other information:

• Have you written new tests for your changes, if applicable?
• Have you checked the E2E test CI results, and verified that your changes do not break them?
• Have you tested your changes on WordPress.com, if applicable (if so, you'll see a generated comment below with a script to run)?

Jetpack product discussion

n/a

Does this pull request change what data or activity we track or use?

no

Testing instructions:

• Before and after patch, setup Jetpack with Sitemaps and publish a post (to trigger sitemap generation or run wp jetpack sitemap rebuild --purge)
• Visit sitemap.xml and view source.
• Without patch, everything after the initial is on line 4.
• With patch, linebreaks are there for it.

[github-actions]

Are you an Automattician? Please test your changes on all WordPress.com environments to help mitigate accidental explosions.

• To test on WoA, go to the Plugins menu on a WordPress.com Simple site. Click on the "Upload" button and follow the upgrade flow to be able to upload, install, and activate the Jetpack Beta plugin. Once the plugin is active, go to Jetpack > Jetpack Beta, select your plugin, and enable the add/line-breaks-sitemap branch.

• To test on Simple, run the following command on your sandbox:

  bin/jetpack-downloader test jetpack add/line-breaks-sitemap
  

Interested in more tips and information?

• In your local development environment, use the jetpack rsync command to sync your changes to a WoA dev blog.
• Read more about our development workflow here: PCYsg-eg0-p2
• Figure out when your changes will be shipped to customers here: PCYsg-eg5-p2

[github-actions]

Thank you for your PR!

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[github-actions]

This PR has been marked as stale. This happened because:

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If this PR is still useful, please do a [trunk merge or rebase](https://github.com/Automattic/jetpack/blob/trunk/docs/git-workflow.md#keeping-your-branch-up-to-date) and otherwise make sure it's up to date and has clear testing instructions. You may also want to ping possible reviewers in case they've forgotten about it. Please close this PR if you think it's not valid anymore — if you do, please add a brief explanation.

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[github-actions]

This PR has been automatically closed as it has not been updated in some time. If you want to resume work on the PR, feel free to restore the branch and reopen the PR.

[github-actions]

Code Coverage Summary

Cannot generate coverage summary while tests are failing. 🤐

Please fix the tests, or re-run the Code coverage job if it was something being flaky.

Full summary · PHP report · JS report

[jeherve]

That's a nice little improvement, and the sitemaps still validate. 🚢